linux-ext4 - Re: Using latest e2fsprogs on various offline VM ext filesystems

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Date:	Sat, 18 Apr 2015 21:30:46 +0100
From:	Daniel Johnson <ukfreebies@...il.com>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Using latest e2fsprogs on various offline VM ext filesystems

Great, thanks Andreas for confirming that, and for the snapshot tip.
Dan

On 18/04/15 16:12, Andreas Dilger wrote:
> You can safely use newer e2fsprogs on older file systems. This should not
> affect compatibility with older kernels in any way, unless you explicitly
> enable features.
>
> Note that if you are using LVM/DM you could create a snapshot of the
> running device and run e2fsck on that. If no errors are found then you
> don't need to stop the VM at all. You can reset the last checked counter
> and mount count via tune2fs. Only if you find an error in the snapshot do
> you need to unmount the filesystem to fix it.
>
> Cheers, Andreas
>
>> On Apr 18, 2015, at 06:46, Daniel Johnson <dan.u.johns@...il.com> wrote:
>>
>> Apologies if this "user" question has been asked before.
>>
>> Tomorrow I will be stopping a couple of dozen kvm virtual machines
>> running various Linux distros and running a forced e2fsck on all of
>> their ext filesystems. The distros are a mix of various flavours of
>> Ubuntu, Debian and Centos, so will include some fs created with older
>> kernels and E2fsprogs.
>>
>> The host is 64-bit Centos 6 running vanilla kernel 3.14.39. I figured
>> I'll build the latest E2fsprogs 1.42.12 for this rather than using the
>> Centos 6 e2fsprogs-1.41.12-21.el6.x86_64.
>>
>> My question is; should it be safe in theory to use the latest
>> E2fsprogs on a mix of ext filesystems in this way? I would have
>> thought so but don't want to rely on any assumptions :-)
>>
>> I'll be setting up device maps on the host server to get to the
>> filesystems on each VMs virtual disk, and doing read only checks. But
>> if anything needs a repair then I could potentially have a fs modified
>> on newer kernel & userspace that then has to boot inside a VM with a
>> distro with much older kernel and userspace such as Centos 5, which is
>> what I'm concerned about.
>>
>> Thanks,
>> Dan
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